A number of automobiles today have McPherson front end suspension systems. These suspension systems are characterized by a McPherson strut that provides both suspension and shock absorbing functions. The strut is susceptible to being bent upon impact of the wheel which can upset the desired wheel caster angle setting, not to mention toe-in and camber settings.
McPherson suspension systems over the years have been adopted primarily in foreign automobiles, but in recent years American automobiles have begun using the McPherson strut system. One example is the 1985 Cadillac, Buick and Oldsmobile front wheel drive automobiles. On many new compact cars, the caster angle is not adjustable. On the 1985 Cadillac, Buick and Oldsmobile, the front wheel caster angle adjustment is difficult. The result is a higher cost of front end alignments because of the increased time the mechanic will need to make a proper caster adjustment; or more customer complaints about poor handling, oversteering, wandering, or wheel hop if the caster adjustment is not made properly.
The McPherson front suspension includes an elongated strut housing extending upwardly through a surrounding suspension spring. A bearing above the strut housing is attached to the underside of a strut mounting plate affixed to the frame of the vehicle. Caster angle is the angle between the axis of the strut and a vertical axis through the center of the wheel. If the strut requires a caster angle adjustment, the top of the strut housing can be moved laterally to change the strut angle. In the McPherson strut assemblies used in the 1985 Cadillac, Buick and Oldsmobile automobiles, this requires loosening the fasteners between the top of the strut assembly and the strut mounting plate, moving the top of the strut in a forward or backward direction to change the caster angle, and tightening the fasteners after the proper caster adjustment is set. However, the factory has not provided a simple means for making the caster adjustment. The 1985 instructional manual informs the mechanic to drill holes on opposite sides of a point at which the top of the strut assembly is attached to the strut mounting plate. The drilled holes then must be filed to form a long slotted hole that will allow the top of the strut assembly to slide relative to the fixed strut mounting plate to make the camber angle adjustment. No information is given on how to move the strut when making the caster angle adjustment. The strut can be moved by hammering on a punch for applying a pushing force to the top of the strut assembly, but this can damage the expensive strut assembly. A large amount of force is required to move the strut because of the weight of the strut assembly, and because the strut is moved against the weight of the vehicle. Moreover, the force must be applied at an awkward angle because of the elevation of a lip on the strut mounting plate which surrounds the top of the strut assembly. This also makes the strut position adjustment difficult.
The present invention provides a tool for making the caster angle adjustment in a McPherson front end suspension system of the type described above.